Developmental Project 2 (Dr. Mark Schnitzer/Dr. Recht-Co-PI's) - Their project will develop a multi-spectral fluorescence endoscope and study fluorescently labeled tumor cells at the cellular level in living rodent brain. This project is an excellent example of a physicist working with a clinical cancer researcher to develop next-generation technology for studying tumor biology. It will provide an entirely new way to study cancer that should lead to many future projects beyond what is in the developmental project. It will likely also impact Research Project #4 (Shawn Chen PI) because it will allow for PET and MRI imaging in that project to eventually be linked to imaging at a much finer resolution scale at the cellular level in this developmental project.